Figure 1 best illustrates effects of the interaction term. For instance, close inspection of these results suggests that at low and moderate levels of nicotine dependence, possessing higher values on the genetic risk score increases risk for relapse. Conversely, at high levels of nicotine dependence, the genetic risk appears to paradoxically protect against relapse (ie, as genetic risk score increases the risk for relapse decreases). This interactive effect is supported in Figure 1 which shows the cumulative incidence of risk for relapse as a function of the median split of both the aggregate genetic risk score (low vs. high risk) and Fagerstrom scores (low vs. high scores on nicotine dependence items). Although this interaction is significant, the confidence interval for Hazard Ratio corresponding to the interaction term is very close to including one and should be interpreted with caution, at least regarding this paradoxical effect. Nonetheless, the finding at low and medium levels of nicotine dependence is notable.
